I did some research online and apparently you need to it’s part of a package that requires a separate install.

The following plug-ins and associated files are included in this package:

• Bigger Tiles
• Picture Package (ContactSheetII)
• ExtractPlus
• PatternMaker
• PhotomergeUI
• TWAIN
• Web Photo Gallery (WebContactSheetII) plus presets
• Textures for Texturizer
• script for Layer Comps to Web Photo Gallery

For Mac users, click here to download. The Windows version can be downloaded from here.

Enjoy